In many industries, such as the food industry, biological R&D, biological pilot plants and production facilities, the handling of fluid products requires an extremely sanitary environment. Equipment designed for product contact must create nonturbulent flow to safeguard products from damage as they travel through the valve. Ideally, a smooth, reliable passageway should be provided that is completely drainable to prevent any entrapment of the fluid material. It is also critical that valves in these industries be able to handle steam-in-place and clean-in-place techniques.
Currently, diaphragm valves are most prevalent in the above industries. Historically these valves have been viewed as sanitary and easy to clean. However, diaphragm valves maintain significant drawbacks in these areas that can be improved upon. For example, diaphragm valves have to be mounted in a specific configuration to permit drainage, which makes them installation sensitive. Second, the diaphragm in diaphragm valves creates a large sealing area which has potential to trap bacteria or leak. U.S. Pat. No. 4,800,920 to Yusko attempts to address the shortcomings of the diaphragm valve by using a pinch valve with an elastomeric sleeve. The Yusko valve, however, has a sleeve that is shorter than the length of the valve body requiring internal connection of the valve to fluid systems. Internal connection areas present the potential for entrapment of fluids and biological material.
An issue with pinch valves that concerns individuals in the aforementioned industries is the reliability of the tubing element or insert. Particularly, closing the valve places the insert tubing under tensile force (ie, repeated flexing or cycling) which wears the insert making it unsafe for use. Several attempts have been made to increase the life of the tubing element. For example, U.S. Pat. No. 3,350,053 to Schmitz describes some of the problems inherent to pinch valves used in the biopharmaceutical industry. In this patent, an attempt is made to increase the cycle life of the tubing element by using a preselected bulge molded into the insert between the end flanges. The sleeve is positioned in an unstretched, slack arrangement and a valve actuating member has a predetermined range of movement that takes up the slack molded into the sleeve. Thus, the sleeve experiences reduced, if any, tensile force as a result of actuator movement to a closed position.
An additional shortcoming of existing valves is their difficulty to be disassembled and cleaned. When the tubing element of a pinch valve or a diaphragm of a diaphragm valve is removed, areas that have been wetted must be cleaned, most often by hand. Hand cleaning results in decreased productivity and potential introduction of foreign agents into the valve and/or process stream.
Yusko's pinch valve features areas that must be cleaned when the tubing sleeve is removed—the parts of the valve that are wetted during operation. Taylor (U.S. Pat. No. 5,657,960) provides a pinch valve with internal gaskets that must be cleaned when the valve is opened and the element is replaced. Ensign's valve (U.S. Pat. No. 4,108,418) must be cleaned as parts are wetted during operation due to the flexible sleeve having a smaller axial length than the length of the valve, such that internal portions of the valve besides the element are wetted while in operation.
Another problem with existing pinch valves is that the flexible tubing element is not manufactured from a high-purity material. Current materials are often toxic elastomers manufactured in unsanitary environments, potentially contaminating products.
Finally, the standard connection type in the biopharmaceutical industry is a tri-clamp connection. The drawback of current tri-clamp designs is that a gasket is required between the valve and the connecting surface. This gasket can act as a bacteria trap, prevent drainage or even cause turbulence in the flow.
The subject of this invention contemplates a new and improved pinch valve arrangement that overcomes all of the above referenced problems of both current pinch valves and diaphragm valves and that provides an extremely reliable valve. While the invention most immediately pertains to the biopharmaceutical industry, it will be appreciated that the invention has broader applications and may be advantageously employed in other environments and applications.